Exact and repeatable metering of dosage units is important for example in the pharmaceutical sector, in order for the patient to take the exact envisaged quantity of an active ingredient. Solid dosage forms can be, for example, pills, or pulverulent quantities or pellets, respectively, that are provided in gelatine capsules. Of course, any other solid-type dosage forms are also to be considered. In any case, the metering of such dosage units is typically performed by volumetric means, wherein a specific target mass is aimed for by way of a specific measured volume and the density of the material. Ultimately, however, it is not the volume but rather the mass of the individual dosage units that is actually achieved in the metering that is important. Density variations in the material, incomplete filling or emptying of the volumetric measuring chamber and the like can lead to undesirable variations in the target mass. A reliable process control is therefore necessary in particular in the case of critical active ingredients.
Various control steps can be considered for controlling a proper sequence of the metering procedure. A first optional control step can be performed via a capacitive measuring section, for example. The latter can produce qualitative statements pertaining to the metering process and assist in locating process errors. Gravimetric measurements in which the dosage units that were previously measured in volumetric terms are individually weighed are performed for quantitative controlling of the metering result. The individual dosage units have to be brought to rest for the static procedure of weighing. However this is in contrast to the high conveying velocities in the case of metering on an industrial scale. Process control to the extent of 100 percent as is occasionally required can thus be implemented only with difficulty and with high expenditure.